Thermoplastic resin composition

ABSTRACT

A thermoplastic resin composition, comprising: 
     (A) 20-95% by weight of a methacrylimide group-containing resin polymer containing at least 5% by weight of an imide ring structural unit expressed by the structural formula (I) ##STR1##  (wherein R 1  is a hydrogen atom or a substituted or non-substituted alkyl group having 1-20 carbon atoms, cycloalkyl group, aryl group, alkaryl group or an aralkyl group or allyl group); 
     (B) 2.5-30% by weight of at least one thermoplastic elastomer selected from the group consisting of polyether esters, polyether ester amides and polyether amides; and 
     (C) 2.5-50% by weight of a graft-copolymer obtained by graft-polymerizing at least one monomer selected from the group consisting of vinyl cyanate monomer, aromatic vinyl monomer and acrylic vinyl monomer to a butadiene rubber, 
     is disclosed. This composition has balanced properties in heat resistance, impact strength and moldability.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a thermoplastic resin composition which has ahigh heat distortion temperature along with excellent impact resistanceand moldability.

2. Description of the Prior Art

The methacrylimide group-containing polymer is known as a thermoplasticresin polymer with excellent properties in heat resistance andtransparency (U.S. Pat. No. 4,246,374). However, its application as amolding material is considerably restricted due to inferior mechanicalproperties including impact strength.

Many attempts have been made to eliminate the drawbacks of themethacrylimide group-containing polymer, proposing various methodsincluding, for example, [1] a method of blendingacrylonitrile-butadiene-styrene copolymer (ABS resin), methylmethacrylate-butadiene-styrene copolymer (MBS resin) or alkyl acrylaterubber as an impact modifier (Laid-Open Japanese Patent Application52-63989), [2] a method of blending a butadiene rubber- or alkylacrylate rubber-base multi-stage polymer in combination withpolycarbonate as an impact modifier (Laid-Open Japanese PatentApplication 55-80459), and [3] a method of blending a butadienerubber-base multi-stage polymer in combination with an alkyl acrylaterubber-base multi-stage polymer as an impact modifier.

Nevertheless, the impact strength obtained by the methods [1] and [3]mentioned above are still insufficient. Namely, it is necessary to blendthe impact modifier in a large quantity to secure a higher impactstrength. This, however, sacrifices the heat resistance inherent to themethacrylimide group-containing polymer as well as its fluidity inmolding. On the other hand, the method [2] which intends to improve theimpact strength while retaining the molding fluidity fails to producethe intended effects to a sufficient degree because the methacrylimidegroup-containing polymer has low compatibility with polycarbonate bynature.

For solving these problems, a proposal has been made with regard to anattempt of improving the impact strength by blending the methacrylimidegroup-containing polymer with a specific thermoplastic elastomerselected from polyether ester, polyether ester amide and polyether amide(Laid-Open Japanese Patent Application 59-49252). Although it ispossible to improve the impact strength and molding fluidity by thismethod, the inherent heat resistance of the methacrylimidegroup-containing polymer has to be sacrificed to enhance the impactstrength further.

Under these circumstances, researches have been conducted with a view toincrease the impact strength of the methacrylimide group-containingpolymer and to improve the moldability without impairing its inherentheat resistance, and as a result it has been found that these objectivescan be attained by blending a specific thermoplastic elastomer and aspecific butadiene rubber graft-copolymer with the methacrylimidegroup-containing polymer.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a thermoplasticresin composition, comprising:

(A) 20-95% by weight of a methacrylimide group-containing polymercontaining at least 5% by weight of an imide ring structural unitexpressed by the structural formula (I) ##STR2## (wherein R₁ is ahydrogen atom or a substituted or non-substituted alkyl group having1-20 carbon atoms, cycloalkyl group, aryl group, alkaryl group or anaralkyl group or allyl group);

(B) 2.5-30% by weight of at least one thermoplastic elastomer selectedfrom the group consisting of polyether ester, polyether ester amide andpolyether amide;

(C) 2.5-50% by weight of a graft-copolymer obtained bygraft-polymerizing at least one monomer selected from the groupconsisting of vinyl cyanate monomer, aromatic vinyl monomer and acrylicmonomer to a butadiene rubber.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For preparing the methacrylimide group-containing polymer in the presentinvention, it is useful to employ a method of reacting a methacrylicresin and ammonia or a primary amine (hereinafter ammonia and primaryamine will be referred to as "an imidizing agent" for brevity) under aninert gas atmosphere and in an inert solvent at a temperature of180°-350° C., preferably at a temperature of 200°-330° C. Nitrogen gasis useful as the inert gas, and the inert solvent is preferred to be asolvent or a mixture of two or more solvents, which is capable ofdissolving the methacrylic resin of the starting material and themethacrylimide group-containing polymer to be produced. Examples ofuseful solvents include aromatic hydrocarbons such as benzene, tolueneand xylene, and aliphatic alcohols such as methanol, ethanol andpropanol.

In the imide ring structural unit mentioned above, R₁ is a hydrogen atomor a substituted or non-substituted alkyl group having 1-20 carbonatoms, cycloalkyl group, aryl group, alkaryl group or an aralkyl groupor allyl group. Among these, a hydrogen atom, a methyl group, an ethylgroup, a t-butyl group, a cyclohexyl group and a phenyl group arepreferred. Examples of the imidizing agent for obtaining the imide ringstructural unit include ammonia, methylamine, ethylamine, t-butylamineand cyclohexylamine.

The methacrylimide group-containing polymer in the present inventionshould contain at least 5% by weight of the imide ring structural unit,preferably in a proportion greater than 20% by weight. When the contentof the imide ring structural unit content is less than 5% by weight,heat resistance of the imide polymer is low.

Examples of the methacrylic resins useful in the present invention forthe preparation of the methacrylimide group-containing polymer includehomopolymer of methyl methacrylate, and copolymers of methylmethacrylate and other methacrylic acid esters, acrylic acid esters,styrene, α-methylstyrene and acrylonitrile.

Examples of other methacrylic acid esters include ethyl methacrylate,propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate,t-butyl methacrylate, cyclohexyl methacrylate and benzyl methacrylate.Examples of other acrylic acid esters include methyl acrylate, ethylacrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butylacrylate, cyclohexyl acrylate and benzyl acrylate.

As the methacrylic resin to be used for the preparation of themethacrylimide group-containing polymer, methyl methacrylatehomopolymer, methyl methacrylate-methyl acrylate copolymer, methylmethacrylate-styrene copolymer are especially preferred. Although thereis no restriction in particular, the content of methyl methacrylate inthese copolymers is preferred to be greater than 70% by weight.

The content of the methacrylimide group-containing polymer in thethermoplastic resin composition according to the present invention is inthe range of 20-95% by weight. If its content is smaller than 20% byweight, it becomes difficult to produce a resin composition withexcellent heat resistance. Conversely, if greater than 95% by weight,the resulting resin composition is not expected to have excellentmechanical properties.

The thermoplastic elastomer to be used in the present invention includesat least one thermoplastic elastomer selected from the group consistingof polyether ester, polyether ester amide and polyether amide, of whichpolyether ester is especially preferable. The "polyether ester"preferably used includes a block copolymer containing polyester with anumber average molecular weight of 1,000-60,000 having more than 80 mol% of its repetitive unit constituted by an alkylene terephthalate unitas a hard segment, and poly (alkyleneoxide) glycol with a number averagemolecular weight of 400-6,000 having more than 80 mol % of itsrepetitive unit constituted by an alkylene oxide unit as a soft segment.The content of the poly (alkyleneoxide) glycol component in theblock-copolymer is preferably in the range of 1-85% by weight, morepreferably in the range of 5-50% by weight. Examples of the polyetherester block-copolymers include polyethylene terephthalate-polyethyleneoxide block-copolymer, polyethylene terephthalate-polytetramethyleneoxide block-copolymer, polytetramethylene terephthalate-polyethyleneoxide block-copolymer, and polytetramethyleneterephthalate-polytetramethylene oxide block-copolymer. The "polyetherester amide" and "polyether amide" include block-copolymers whichcontain polyether as a soft segment and polyester amide or polyamide asa hard segment, which can be produced by known processes (Laid-OpenJapanese Patent Application 59-49252).

The content of the thermoplastic elastomer in the thermoplastic resincomposition according to the present invention should be in the range of2.5-30% by weight because it becomes difficult to obtain a resincomposition with the excellent mechanical properties when its content issmaller than 2.5% by weight. When its content is greater than 30% byweight, a difficulty is encountered in obtaining a resin compositionwhich is excellent in balance of the mechanical properties and the heatresistance.

The graft-copolymer useful in the present invention is a graft-copolymerwhich is produced by graft-polymerizing at least one monomer selectedfrom the group consisting of cyanated vinyl monomer, aromatic vinylmonomer and acrylic vinyl monomer to a butadiene rubber. Specificexamples of such graft-copolymers includeacrylonitrile-butadiene-styrene copolymer (ABS resin), methylmethacrylate-butadiene-styrene copolymer (MBS resin) andgraft-copolymers of acrylonitrile and styrene toethylene-propylene-diene rubber (AES resin).

The content of the above-described graft-copolymer in the thermoplasticresin composition of the invention is in the range of 2.5-50% by weight.If its content is less than 2.5% by weight, production of a resincomposition with excellent mechanical properties becomes difficult, and,if in excess of 50% by weight, it is difficult to obtain a resincomposition which has excellent balance in the heat resistance andmechanical properties.

A thermoplastic resin composition of the present invention may beadmixed with other polymers for the purpose of adjusting the resincomposition to secure desired properties.

In the present invention, the methacrylimide group-containing polymer(A), thermoplastic elastomer (B) and graft-copolymer (C) can be blendedby melting and mixing the respective components with granular, powderyor chip shape in a V-type blender, super mixer or kneader, and thenmolding them.

In order to improve the resistance to heat, rays of light, and oxidativedeteriorations, the thermoplastic resin composition of the presentinvention may be added with a heat stabilizer, an antioxidant, anultraviolet ray absorbent or the like. Further, a plasticizer, apigment, a lubricant or the like may be blended into the composition ifdesired. Fibrous material such as glass fibers and carbon fibers mayalso be added for the purpose of reinforcement.

The thermoplastic resin composition of the present invention can beformed into articles of various shapes by compression molding, injectionmolding, extrusion molding or other known plastics molding processes.

EXAMPLES

The present invention will now be described in more detail withreference to Examples, but the present invention is not limited to them.

In the following Examples, the units "part" and "%" indicate "part byweight" and "percentage by weight", respectively, unless otherwiseindicated.

The physical properties of the polymers in Examples were measured by thefollowing methods.

(1) The heat distortion temperature was measured according to ASTM D648(load: 18.6 kg/cm²).

(2) Izod impact strength was measured according to ASTM D256-56 MethodA.

(3) The melt index was determined according to ASTM D1238 (grams for 10minutes at 260° C. under a load of 10 kg).

(4) The imidizing degree (mol %) of the methacrylimide group-containingpolymer was measured from the nitrogen content obtained from theelementary analysis (using a CHN corder (MT-3), a product of YanagimotoSeisakusho K.K.) and from the measurement by proton NMR JNM-FX-100(JEOL) spectrometer at 100 MHz.

(5) The intrinsic viscosity of the polymer was determined by measuringthe flow time (ts) of sample polymer solutions in chloroform indifferent polymer concentration and the flow time (to) of chloroform atthe temperature of 25° C.±0.1° C. with use of Deereax-Bishoffviscometer, calculating the relative viscosity ηrel of the polymer fromthe value of ts/to, and calculating the value of intrinsic viscosityaccording to the following formula. ##EQU1## (wherein C is the grams ofthe polymer per 100 ml of solvent.)

REFERENTIAL EXAMPLE A Preparation of Methacrylimide Group-containingPolymer REFERENTIAL EXAMPLE A-1

100 parts of sufficiently dried methyl methacrylate polymer (Acrypet®VH, a product of Mitsubishi Rayon Co., Ltd. with an intrinsic viscosityof 0.51), 90 parts of toluene and 10 parts of methanol were put in a 10lreactor with a paddle spiral stirrer, pressure gauge, sample injectionvessel and jacket heater, and, after sufficient replacement by nitrogen,the mixture was heated to 250° C. with stirring to dissolve the polymer.Then, 21.7 parts of methylamine (0.7 in molar ratio) were added from thesample injection vessel, and the reaction was effected for 3 hours withheating under an internal pressure of 60 kg/cm² in gauge pressure. Uponcompletion of the reaction, the methacrylimide group-containing polymerA-1 was obtained.

REFERENTIAL EXAMPLE A-2

The procedures in Referential Example A-1 were repeated except thatammonia was used in place of methylamine in an amount corresponding to amolar ratio of 0.8, obtaining the methacrylimide group-containingpolymer A-2 after the reaction.

Table 1 below shows the results of measurements of the imidizationdegree and heat distortion temperatures of the polymers A-1 and A-2.

                  TABLE 1                                                         ______________________________________                                        Imidizing Agent  Imidization                                                                             Heat                                               Polymers        Molar    Degree  Distortion                                   A      Kind     Ratio    (mol %) Temperature (°C.)                     ______________________________________                                        A-1    Methyl-  0.7      70      150                                                 amine                                                                  A-2    Ammonia  0.8      75      197                                          ______________________________________                                    

REFERENTIAL EXAMPLE B Preparation of thermoplastic elastomer (Elastomerswere prepared in accordance with Examples of Laid-Open Japanese PatentApplication 59-49252) REFERENTIAL EXAMPLE B-1 Preparation of polyetherester block copolymer

94.5 parts of dimethyl terephthalate, 41.5 parts of dimethylisophthalate, 38.5 parts of poly (tetramethyleneoxide) glycol with anumber average molecular weight of about 1000 and 94.5 parts of1,4-butandiol were charged into a reactor with a helical ribbon typestirrer, along with 0.1 part of titanium tetrabutoxide catalyst, andheated at 210° C. for 2 hours while distilling 95% of the theoreticalamount of methanol out of the system. 0.42 parts of "Irganox 1010" (anantioxidant produced by Chiba Geigy Co., Ltd.) was then added to thereaction mixture and the temperature was raised to 245° C., thereafterdepressurizing the system to 0.2 mmHg over a time length of 50 minutesand conducting the polymerization for 2 hours under these conditions toobtain a polyether ester block-copolymer.

REFERENTIAL EXAMPLE B-2 Preparation of polyether ester amideblock-copolymer

54.6 parts of ω-aminododecanoic acid, 13.4 parts of dodecanedioic acidand 38.7 parts of poly (tetramethyleneoxide) glycol with a numberaverage molecular weight of 663 were charged into a reactor with ahelical ribbon type stirrer along with 0.2 parts of "Irganox 1098" (anantioxidant produced by Chiba Geigy Co., Ltd.) and 0.05 parts oftetrabutyl titanate catalyst, and, after sufficient replacement bynitrogen, the charged mixture was heated at 220° C. with stirring for 30minutes, obtaining a uniform transparent solution. The solution was thensubjected to reaction for 5 hours and 30 minutes under a polymerizationcondition of 250° C. and 1 mmHg to obtain a molten polymer of acolorless transparent polyether ester amide block copolymer.

REFERENTIAL EXAMPLE B-3 Preparation of polyether amide block-copolymer

136 parts of ε-caprolactam, 38.5 parts of poly (tetramethyleneoxide)glycol with a number average molecular weight of about 1000 and 94.5parts of 1,4-butadiol were charged into a reactor with a helical ribbontype stirrer along with 0.1 part of titanium tetrabuthoxide catalyst,and subjected to reaction under the same conditions as in ReferentialExample B-2, obtaining a polyether amide block copolymer.

REFERENTIAL EXAMPLE C Preparation of Graft-Copolymer REFERENTIAL EXAMPLEC-1 Preparation of acrilonitrile-butadiene-styrene copolymer (ABS resin)

80 parts of polybutadiene latex (with solid content of 50%, averageparticle size of 0.35μ and gel content of 90%), 1 part of sodiumstearate, 0.1 part of sodium formaldehyde sulfoxylate, 0.03 parts oftetrasodium ethylenediaminetetraacetic acid, 0.003 parts of ferroussulfate and 200 parts of water were charged into a reactor, and heatedto 65° C., then adding, continuously over a time length of 4 hours, 60parts of a monomer mixture consisting of 30% of acrylonitrile and 70% ofstyrene, 0.3 parts of t-dodecylmercaptan and 0.2 parts of cumenehydroperoxide. After the addition, the polymerization was conducted at65° C. for 2 hours. Polymerization degree was 96%. After adding anantioxidant to latex, the latex was coagulated with sulfuric acid, andwashed with water and dried to obtain a powderyacrylonitrile-butadiene-styrene copolymer.

REFERENTIAL EXAMPLE C-2 Preparation of methylmethacrylate-butadiene-styrene copolymer (MBS resin)

The procedures of Referencial Example C-1 were repeated for the reactionexcept that 60 parts of a monomer mixture of 70% methyl methacrylate and30% styrene was used in place of 60 parts of the monomer mixture ofacrylonitrile and styrene, finally obtaining a powdery methylmethacrylate-butadiene-styrene copolymer.

EXAMPLES 1-10 & COMPARATIVE EXAMPLES 1-5

The methacrylimide group-containing polymers A-1 and A-2 prepared inReferential Examples A, the thermoplastic elastomers B-1 to B-3 preparedin Referential Examples B, and the graft-copolymers C-1 and C-2 preparedin Referential Examples C were blended in the proportions as indicatedin Table 2, and each one of the resulting resin compositions was meltedand extruded into pellets by an extruder. The pellets were molded byinjection molding to obtain specimens for measurement of physicalproperties. The results of the measurement of physical properties ofthese specimens are also shown in Table 2.

As clear from Table 2, specimens obtained in Examples 1 to 10 areexcellent in the heat distortion temperature, Izod impact strength andfluidity in a balanced fashion, while in the cases where themethacrylimide group-containing polymer alone was used (ComparativeExamples 3 and 4), and where the methacrylimide group-containing polymerand the thermoplastic elastomer or the graft-copolymer were used at ablending ratio outside the range of the invention (Comparative Examples1, 2 and 5), only specimens having insufficient either in Izod impactstrength or in fluidity can be obtained.

                                      TABLE 2                                     __________________________________________________________________________           Blending ratio                                                                       Thermoplastic   Heat  Izod                                                    Elastomers                                                                            Graft-  Distortion                                                                          Impact                                           Polymers A                                                                           B       Copolymers C                                                                          Temp. Strength                                                                             Melt Index                                Type                                                                              Part                                                                             Type                                                                              Part                                                                              Type                                                                              Part                                                                              (°C.)                                                                        (kg · cm/cm.sup.2)                                                          (g/10 min.)                        __________________________________________________________________________    Example                                                                       1      A-1 70 B-1 15  C-1 15  135   23     18                                 2      A-1 70 B-2 15  C-1 15  137   20     17                                 3      A-1 70 B-3 15  C-1 15  139   17     17                                 4      A-1 70 B-1 15  C-2 15  136   18     17                                 5      A-1 70 B-2 15  C-2 15  138   16     16                                 6      A-1 70 B-3 15  C-2 15  140   15     16                                 7      A-2 70 B-1 15  C-1 15  170   10      8                                 8      A-1 80 B-1 10  C-1 10  143   13     10                                 9      A-1 60 B-1 15  C-1 25  130   27     20                                 10     A-1 50 B-1 15  C-1 35  125   30     25                                 Compar. Ex.                                                                   1      A-1 70 B-1 30  --      130    6     15                                 2      A-1 70 --      C-1 30  135    9     13                                 3      A-1 100                                                                              --      --      150    1      8                                 4      A-2 100                                                                              --      --      197    1      3                                 5      A-1 96 B-1  2  C-1  2  147    2     10                                 __________________________________________________________________________

What we claim:
 1. A thermoplastic resin composition, comprising:(A)20-95% by weight of a methacrylimide group-containing polymer containingat least 5% by weight of an imide ring structural unit expressed by thestructural formula (I) ##STR3## (wherein R₁ is a hydrogen atom or asubstituted or non-substituted alkyl group having 1-20 carbon atoms,cycloalkyl group, aryl group, alkaryl group or an aralkyl group or allylgroup); (B) 5-30% by weight of at least one thermoplastic elastomerselected from the group consisting of polyether esters, polyether esteramides and polyether amides; and (C) 2.5-50% by weight of agraft-copolymer obtained by graft-polymerizing at least one monomerselected from the group consisting of vinyl cyanate monomer, aromaticvinyl monomer and acrylic monomer to a butadiene rubber.
 2. Athermoplastic resin composition as claimed in claim 1 wherein thethermoplastic elastomer of the component (B) is a block-copolymer ofpolyether ester, polyether ester amide or polyether amide.
 3. Athermoplastic resin composition as claimed in claim 1 wherein thethermoplastic elastomer of the component (B) is polyetheyleneterephthalate-polytetramethylene oxide block-copolymer.
 4. Athermoplastic resin composition as claimed in claim 1 wherein thegraft-copolymer of the component (C) is acrylonitrile-butadiene-styrenecopolymer.
 5. A thermoplastic resin composition as claimed in claim 1wherein the graft-copolymer of the component (C) is methylmethacrylate-butadiene-styrene copolymer.